THEORETICAL STUDIES ON THE STRUCTURES AND SPECTROSCOPIC PROPERTIES OF IR COMPLEXES WITH THE BIPYRIDYL-PHENYLENEDIAMINE LIGAND

Jianpo Zhang, Ying Wang, Junbo Zang, Yuhe Miao, Yue Sun, Li Jin

ABSTRACT:The phosphorescent iridium(III) complexes (N^C)2Ir(bpy-D) (bpy-D = 4-(N-(2-amino-5- methoxy- phenyl)aminomethyl)-4’-methyl-2,2’-bipyridine: N^C = F-ppy(1), ppy(2), pq(3) , pqe(4); F-ppy = 2-(2,4-difluorophenyl)pyridine, ppy = 2-phenylpyridine, pq = 2-phenylquinoline, pqe = 2-phenylcinchoninic acid methyl ester) were explored using density functional theory (DFT) methods. The optimized geometry structural parameters of the complexes in the ground state agree well with the corresponding experimental values. The lower-lying unoccupied molecular orbitals of complexes 1-4 are dominantly localized on the bidentate ligand, while the higher-lying occupied ones are also composed of bidentate ligand. The lowest energy absorptions at 513, 506, 526, and 569 nm are attributed to a ππ* transition, while their phosphorescence emission at 551, 619, 642, and 659 nm have similar transition properties. This indicates that the phosphorescent color of lowest-energy emissions of these complexes could be tuned, could be altered by adjusting the π electron-donating ability of N^C ligand.

Keywords:Iridium (III) complexes, Spectroscopic properties, Electronic Structures, TD-DFT